Field of the invention
The present disclosure relates to a method of estimating an equivalent model parameter of a transducer and a sonar system using the same, and more particularly, to a method of estimating an equivalent model parameter of a transducer in which a case where a mutual impedance interference effect between adjacent resonant modes of a multi-mode transducer is large and the interference contributions thereof are different is taken into consideration, and a sonar system using the same.
Description of the Related Art
An active sonar system is a system for transmitting underwater acoustic waves and detecting signals reflected from a target, and the detection performance may be dependent upon how large acoustic output power is transmitted in a desired direction. Accordingly, the characteristic of an electrical impedance of the transducer which is a load should be first correctly specified for the purpose of the design of a high output power transmitter constituting an active sonar. Furthermore, an impedance matching circuit corresponding to an interfacing circuit between transmitter-transducer is very important to effectively transmit the maximum power from the transmitter to the load. If the impedance characteristic of a transducer is expressed as an electrical equivalent model, then it may be possible to obtain integrated model for a transmitter-matching circuit-transducer which is a primary constituent element of the active sonar, thereby allowing an effective design and analysis.
Equivalent modeling for a transducer in the related art has been primarily limited to a narrow-band single-mode transducer with no interference of adjacent resonant modes but equivalent modeling for a multi-mode transducer in which there exist several resonant modes within a broadband has been difficult to obtain correct estimation with an analytical method due to a mutual effect of adjacent resonant modes. As an equivalent modeling method for the multi-mode transducer, there have been proposed a method of deriving an approximate equation from the slope of measured admittance and resonant frequency information for each resonant mode and obtaining an equivalent model parameter from it, and the like, but it has a disadvantage that an interference effect between adjacent resonant modes is not taken into consideration and thus the estimation error is very large. In order to overcome the foregoing problem, an optimization method has been applied thereto, but in case of a resonant mode having a relatively small impedance contribution among adjacent resonant modes, it has a problem that the estimation of a resonant mode is impossible or there occurs a failure for the resonant frequency of the estimated mode. Furthermore, it has a problem that a complex calculation is required to derive an initial value during the process of estimating an equivalent model parameter from impedance data, and the estimation result is largely dependent upon the initial value.